1. Field of the Invention
The invention relates to a communication system. More particularly, the invention relates to a method and an apparatus for modulation recognition in a communication system.
2. Description of Related Art
A plurality of different modulation techniques can be applied in a communication system (for example, a digital video broadcasting-cable (DVB-C) system), so that a receiving end of the communication system must be able to correctly recognize a modulation type. Generally, modulation recognition algorithms can be divided into two main types such as pattern recognition and maximum likelihood (ML) recognition. The pattern recognition is to obtain high-order statistics data or an envelop of a signal, so as to present characteristics of different modulation signals. However, implementation of the pattern recognition is complicated. Moreover, in a noisy environment, performance of the pattern recognition is decreased. The ML recognition is performed under a premise of maximum likelihood or log likelihood. In the noisy environment, a low convergence rate of the ML recognition requires to receive a large amount of monitoring samples of data.